Use container::back() and container::pop_back() in ui/

ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc

Index: ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc
diff --git a/ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc b/ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc
index 65388a2e7589b01b88ba1db503353d8c161c4146..b1d46cef76b7db63c06f45f38cea64376e7df924 100644
--- a/ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc
+++ b/ui/events/ozone/evdev/libgestures_glue/event_reader_libevdev_cros.cc
@@ -20,8 +20,8 @@ namespace {
 
 std::string FormatLog(const char* fmt, va_list args) {
   std::string msg = base::StringPrintV(fmt, args);
-  if (!msg.empty() && msg[msg.size() - 1] == '\n')
-    msg.erase(msg.end() - 1, msg.end());
+  if (!msg.empty() && msg.back() == '\n')
+    msg.pop_back();
   return msg;
 }